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doc: add child node monitoring example

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Ian Barwick
2019-04-24 16:04:47 +09:00
parent c092ce60a7
commit da24896fd5
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doc/repmgrd-automatic-failover.sgml
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@@ -269,7 +269,46 @@
<sect2 id="repmgrd-primary-child-disconnection-example">
<title>Standby disconnections monitoring process example</title>
<para>
This example shows typical <application>repmgrd</application> log output from a three-node cluster
(primary and two child nodes), with <varname>child_nodes_connected_min_count</varname>
set to <literal>2</literal>.
</para>
<para>
<application>repmgrd</application> on the primary has started up, while two child
nodes are being provisioned:
<programlisting>
[2019-04-24 15:25:33] [INFO] monitoring primary node "node1" (node ID: 1) in normal state
[2019-04-24 15:25:35] [NOTICE] new node "node2" (node ID: 2) has connected
[2019-04-24 15:25:35] [NOTICE] 1 (of 1) child nodes are connected, but at least 2 child nodes required
[2019-04-24 15:25:35] [INFO] no child nodes have detached since repmgrd startup
(...)
[2019-04-24 15:25:44] [NOTICE] new node "node3" (node ID: 3) has connected
[2019-04-24 15:25:46] [INFO] monitoring primary node "node1" (node ID: 1) in normal state
(...)</programlisting>
</para>
<para>
One of the child nodes has disconnected; <application>repmgrd</application>
is now waiting <varname>child_nodes_disconnect_timeout</varname> seconds
before executing <varname>child_nodes_disconnect_command</varname>:
<programlisting>
[2019-04-24 15:28:11] [INFO] monitoring primary node "node1" (node ID: 1) in normal state
[2019-04-24 15:28:17] [INFO] monitoring primary node "node1" (node ID: 1) in normal state
[2019-04-24 15:28:19] [NOTICE] node "node3" (node ID: 3) has disconnected
[2019-04-24 15:28:19] [NOTICE] 1 (of 2) child nodes are connected, but at least 2 child nodes required
[2019-04-24 15:28:19] [INFO] most recently detached child node was 3 (ca. 0 seconds ago), not triggering "child_nodes_disconnect_command"
[2019-04-24 15:28:19] [DETAIL] "child_nodes_disconnect_timeout" set To 30 seconds
(...)</programlisting>
</para>
<para>
<varname>child_nodes_disconnect_command</varname> is executed once:
<programlisting>
[2019-04-24 15:28:49] [INFO] most recently detached child node was 3 (ca. 30 seconds ago), triggering "child_nodes_disconnect_command"
[2019-04-24 15:28:49] [INFO] "child_nodes_disconnect_command" is:
"/usr/bin/fence-all-the-things.sh"
[2019-04-24 15:28:51] [NOTICE] 1 (of 2) child nodes are connected, but at least 2 child nodes required
[2019-04-24 15:28:51] [INFO] "child_nodes_disconnect_command" was previously executed, taking no action</programlisting>
</para>
</sect2>
<sect2 id="repmgrd-primary-child-disconnection-configuration">
@@ -319,6 +358,12 @@
to be executed by the system user under which the PostgreSQL server itself
runs (usually <literal>postgres</literal>).
</para>
<note>
<para>
If <varname>child_nodes_disconnect_command</varname> is not set, no action
will be taken.
</para>
</note>
<para>
If specified, the following format placeholder will be substituted when
executing <varname>child_nodes_disconnect_command</varname>: